What is receipt number?

Hi,

I would like to know about Receipt number. Please anyone help me to know this.
In schedule appointment, I completed till step 8. After that, I am not able to proceed to pay.
Please tell me how to pay and get the receipt number.
Once I click 'BOA' in Electronic using NEFT, I got Unique Account number.
From this I understood I can transfer amount from my own bank to this account number.
Now anyone please explain me where can I get the receipt number. Is this the one after our bank transaction completes, we get a payment confirmation number?
I am not clear on this. How our bank and US visa site interconnected for receipt number?
Will I get a mail regarding this? Because of this I am not able to book the appointment
Please help me.